WO2023196364A1 - Acid-base mediated ion-exchange metal loaded zeolite - Google Patents
Acid-base mediated ion-exchange metal loaded zeolite Download PDFInfo
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- WO2023196364A1 WO2023196364A1 PCT/US2023/017511 US2023017511W WO2023196364A1 WO 2023196364 A1 WO2023196364 A1 WO 2023196364A1 US 2023017511 W US2023017511 W US 2023017511W WO 2023196364 A1 WO2023196364 A1 WO 2023196364A1
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- zeolite
- solution
- ammonium
- slurry
- molybdate
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- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 title claims abstract description 62
- 239000010457 zeolite Substances 0.000 title claims abstract description 62
- 229910021536 Zeolite Inorganic materials 0.000 title claims abstract description 59
- 238000005342 ion exchange Methods 0.000 title claims abstract description 14
- 230000001404 mediated effect Effects 0.000 title claims abstract description 9
- 229910052751 metal Inorganic materials 0.000 title claims description 21
- 239000002184 metal Substances 0.000 title claims description 21
- 238000000034 method Methods 0.000 claims abstract description 39
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 37
- 239000003054 catalyst Substances 0.000 claims abstract description 35
- 239000011733 molybdenum Substances 0.000 claims abstract description 34
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims abstract description 30
- -1 molybdenum ions Chemical class 0.000 claims abstract description 24
- 238000012544 monitoring process Methods 0.000 claims abstract description 3
- 238000007792 addition Methods 0.000 claims description 36
- 239000002002 slurry Substances 0.000 claims description 31
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 21
- 239000011148 porous material Substances 0.000 claims description 20
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 18
- 239000000908 ammonium hydroxide Substances 0.000 claims description 18
- APUPEJJSWDHEBO-UHFFFAOYSA-P ammonium molybdate Chemical compound [NH4+].[NH4+].[O-][Mo]([O-])(=O)=O APUPEJJSWDHEBO-UHFFFAOYSA-P 0.000 claims description 16
- 239000011609 ammonium molybdate Substances 0.000 claims description 13
- 235000018660 ammonium molybdate Nutrition 0.000 claims description 13
- 229940010552 ammonium molybdate Drugs 0.000 claims description 13
- 229910052742 iron Inorganic materials 0.000 claims description 11
- 239000002245 particle Substances 0.000 claims description 7
- 239000011684 sodium molybdate Substances 0.000 claims description 7
- TVXXNOYZHKPKGW-UHFFFAOYSA-N sodium molybdate (anhydrous) Chemical compound [Na+].[Na+].[O-][Mo]([O-])(=O)=O TVXXNOYZHKPKGW-UHFFFAOYSA-N 0.000 claims description 7
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 6
- 235000015393 sodium molybdate Nutrition 0.000 claims description 6
- 235000019270 ammonium chloride Nutrition 0.000 claims description 3
- QGAVSDVURUSLQK-UHFFFAOYSA-N ammonium heptamolybdate Chemical compound N.N.N.N.N.N.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.[Mo].[Mo].[Mo].[Mo].[Mo].[Mo].[Mo] QGAVSDVURUSLQK-UHFFFAOYSA-N 0.000 claims description 3
- 229910000323 aluminium silicate Inorganic materials 0.000 claims description 2
- 229910019934 (NH4)2MoO4 Inorganic materials 0.000 claims 1
- 229910004619 Na2MoO4 Inorganic materials 0.000 claims 1
- 230000008569 process Effects 0.000 abstract description 7
- 230000002378 acidificating effect Effects 0.000 abstract description 6
- 238000005516 engineering process Methods 0.000 abstract description 5
- 229910052782 aluminium Inorganic materials 0.000 abstract description 3
- 230000003197 catalytic effect Effects 0.000 abstract description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 abstract description 2
- 230000009849 deactivation Effects 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 35
- 239000000243 solution Substances 0.000 description 35
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 32
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 28
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 23
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 19
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 18
- 238000006243 chemical reaction Methods 0.000 description 15
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 11
- 239000003153 chemical reaction reagent Substances 0.000 description 9
- 239000011343 solid material Substances 0.000 description 9
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 8
- 229910017604 nitric acid Inorganic materials 0.000 description 8
- 230000002572 peristaltic effect Effects 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Chemical compound O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 description 6
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 5
- 238000011068 loading method Methods 0.000 description 5
- 150000002739 metals Chemical class 0.000 description 5
- 229910052697 platinum Inorganic materials 0.000 description 5
- 239000007787 solid Substances 0.000 description 5
- 229910019142 PO4 Inorganic materials 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 239000002253 acid Substances 0.000 description 4
- 229930195733 hydrocarbon Natural products 0.000 description 4
- 150000002430 hydrocarbons Chemical class 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000000725 suspension Substances 0.000 description 4
- 229910015667 MoO4 Inorganic materials 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 239000000706 filtrate Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 150000001450 anions Chemical class 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 150000001491 aromatic compounds Chemical class 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- 239000003245 coal Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 2
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 2
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 239000003208 petroleum Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- 239000012494 Quartz wool Substances 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000004873 anchoring Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 150000004945 aromatic hydrocarbons Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000001833 catalytic reforming Methods 0.000 description 1
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 1
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007323 disproportionation reaction Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000002638 heterogeneous catalyst Substances 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 159000000014 iron salts Chemical class 0.000 description 1
- 229910000360 iron(III) sulfate Inorganic materials 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910001960 metal nitrate Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910000476 molybdenum oxide Inorganic materials 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- PQQKPALAQIIWST-UHFFFAOYSA-N oxomolybdenum Chemical compound [Mo]=O PQQKPALAQIIWST-UHFFFAOYSA-N 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 239000002304 perfume Substances 0.000 description 1
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 125000002467 phosphate group Chemical group [H]OP(=O)(O[H])O[*] 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000012041 precatalyst Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000005588 protonation Effects 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000004230 steam cracking Methods 0.000 description 1
- 230000035899 viability Effects 0.000 description 1
- 239000012690 zeolite precursor Substances 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/03—Precipitation; Co-precipitation
- B01J37/031—Precipitation
- B01J37/035—Precipitation on carriers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/03—Precipitation; Co-precipitation
- B01J37/031—Precipitation
- B01J37/033—Using Hydrolysis
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
- B01J29/48—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing arsenic, antimony, bismuth, vanadium, niobium tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- B01J31/26—Catalysts comprising hydrides, coordination complexes or organic compounds containing in addition, inorganic metal compounds not provided for in groups B01J31/02 - B01J31/24
- B01J31/34—Catalysts comprising hydrides, coordination complexes or organic compounds containing in addition, inorganic metal compounds not provided for in groups B01J31/02 - B01J31/24 of chromium, molybdenum or tungsten
-
- B01J35/40—
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
- B01J2531/60—Complexes comprising metals of Group VI (VIA or VIB) as the central metal
- B01J2531/64—Molybdenum
Definitions
- Aromatic compounds are important building blocks of pharmaceuticals, polymers, paints, dyes, explosives, perfumes, and many other materials.
- Benzene may be the most well-known aromatic compound. Most common methods of production of benzene are not friendly towards the environment, and often require harsh reaction conditions (high temperature, pressure), and the use of expensive catalysts.
- This alternative method could utilize methane that is lost due to flaring and leaks. This could potentially have more positive impact on the environment by creating an economically productive disposition for methane. More importantly, the proposed method described herein would place the US in a position of benzene exporter and create an enduring economic benefit.
- Heterogeneous catalysts are used in a vast number of chemical and petrochemical processes. In many cases, the viability of the process depends on the successful combination of the activity of the catalyst and its selectivity and stability. A catalyst that has a high activity but exhibits poor selectivity to the desired products might not be useful to implement a chemical reaction in a commercial scale. Furthermore, a catalyst having a good activity and a good selectivity to the desired product but showing a poor stability may not be suitable for industrial application. An optimum balance between activity, selectivity and stability must be achieved in order to consider the practical application of a catalyst.
- clusters Small metal or metal oxide particles having diameters in the nanoscale range are often referred to as clusters.
- Zeolitic materials are unique supports for metal clusters because the steric restrictions imparted by their cages and pores limit the size of the clusters that can form in them.
- the restrictions imparted by the apertures (often termed “windows”) between cages and pores limit the size of what can enter and leave the pores and cages.
- clusters can be formed from small precursors (e.g. metal salts) in the cages and be trapped there.
- the cages of zeolitic materials are small enough to exert solvent-like effects on clusters formed within them and thus the cages may induce different catalytic properties to the clusters they contain. Confinement of clusters in zeolitic material cages hinders cluster interactions and aggregation and thereby increase cluster stability.
- Supported metal and metal oxide cluster catalysts can be prepared in a number of different ways.
- the technology described herein relates to a novel simultaneous addition method for producing molybdenum zeolite cluster catalysts.
- Molybdenum ions uniformly dispersed inside zeolite channels and located in proximity to the acidic aluminum sites, lead to high catalytic activity and resistance to deactivation in the methane dehydroaromatization process. It is also known that molybdenum solubility varies with pH, with a minimum of around 1.5.
- a typical procedure is to slurry zeolite ZSM-5 with HC1 at a pH of about 0 - 1, and separately prepare a solution of ammonium molybdate with ammonium hydroxide at a pH of 8 - 11, and then simultaneously introduce the prepared slurry and solution into an ammonium chloride solution at a desirable pH, typically 0.5 - 6.5, where the pH is continually monitored and held constant throughout the procedure by adjusting the relative rates of the slurry and solution throughout the addition.
- This technique is typically referred to as “simultaneous addition” and is regularly used in the chemical industry to produce a consistent product due to the fact that the reaction conditions are maintained and consistent throughout the process.
- the resulting slurry is filtered and the filtrate is analyzed for molybdenum content.
- the solid is dried, calcined and analyzed for molybdenum content.
- anywhere from 1 - 75% of the molybdenum from the initial solution carries through to the filtrate.
- the amount of molybdenum in the filtrate is low, it is assumed to be incorporated into the zeolite.
- this technology is a method of preparing a supported catalyst, comprising the steps of: providing a porous catalyst support comprising a framework having an internal pore structure comprising one or more pores where the internal pore structure comprises a precipitant; adding to the catalyst support a solution or slurry comprising catalytically active molybdate anions such that, on contact with the precipitant, particles comprising the catalytically active metal are precipitated within the internal pore structure of the framework of the catalyst support; and, monitoring the solution pH and adjusting the relative rates of the catalytically active molybdate anions throughout the addition.
- the catalyst support is typically an aluminosilicate zeolite comprising zeolite channels within the internal pore structure of the framework, and the molybdate anions may be ammonium molybdate anions, which are added to the zeolite channels via a simultaneous acid-base mediated ion exchange process.
- the zeolites may be HZSM- 5 or NH4ZSM-5.
- one or more elements selected from the group consisting of iron and platinum may also be used.
- the ammonium molybdate anions may be clusters and have an effective diameter of less than 5.0 nm or less the 2.0 nm.
- the pH of ammonium molybdate solution or slurry is from 7 to at least 10 and the zeolite is acidified to maintain a desired pH during the ion exchange process, where the zeolite may be acidified with HC1 to a pH of about 0 - 1.
- a solution of ammonium molybdate and ammonium hydroxide is prepared to a pH of 8 - 11 , and is simultaneously introduced to a prepared zeolite slurry or solution into an ammonium chloride solution at a pH of 0.5 - 6.5, and where pH is continually monitored and held constant by adjusting the relative rates of slurry and solution throughout the addition.
- the molybdenum ion source is selected from the group consisting of ammonium orthomolybdate, ammonium heptamolybdate, or sodium molybdate,
- Figure 1 SEM-EDS images of (left) acid-form zeolite ZSM-5, starting material, and (right) molybdenum-modified zeolite ZSM-5 prepared by acid-base mediated ionexchange.
- Figure 2 Different forms of molybdate anions in aqueous solutions depending on the pH and concentration. (Reprinted from Davantes, A.; Lefevre, G. J. Phys. Chem. A 2013, 117, 12922-12929)
- FIG. Activity Data for 8Mo-0.5Fe/HZSM-5 (Example 1), 2Mo/HZSM-5 (Example 4), and 12Mo/HZSM-5 (Example 5).
- the internal pore structure of the framework of the catalyst support can be loaded by post-treatment of the catalyst support.
- the result is a catalyst support in which precipitant is located within the internal pore structure of the framework.
- the solution or colloidal suspension enters the internal porous structure of the catalyst support framework and, on contact with precipitant, precipitation or formation of insoluble particles occurs, which particles comprise the catalytically active metal.
- particles comprising the catalytically active metal are referred to herein as “clusters”.
- clusters typically have effective diameters of less than 5.0 nm, more preferably less than 2.0 nm, for example less than 1.3 nm.
- the maximum dimension or effective diameter of the cluster is defined by the internal pore structure of the catalyst support framework.
- the catalytically active metal can be dissolved in a solution, or can be a constituent of a colloid in suspension, or both.
- the catalyst support can be crystalline or amorphous, with a preference for crystalline supports due to their well-defined pore structure and generally greater stability.
- the catalyst support is preferably an inorganic support, and more preferably an oxide support.
- oxide supports include silica, alumina, zirconia, titania, ceria, lanthanum oxide, and mixed oxides thereof, such as alumina-silica.
- Other examples of catalyst supports include those having extended phosphate structures, for example alumino- phosphates, a gallo-phosphates, silico-alumino-phosphates and silico-gallo-phosphates.
- the catalyst support is preferably an oxide material having a zeotype structure, exemplified by zeolites.
- zeotype structures Numerous zeotype structures are known, and are described in the “Atlas of Zeolite Structures” published and maintained by the International Zeolite Association.
- Preferred structures are those having a 2-dimensional or 3-dimensional porous network, intersecting at cages having a diameter larger than that of the pores. Examples of zeotype structures having such a 2-dimensional and 3-dimensional pore configuration include CHA, FAU, BEA, MFI, MEL and MWW. 3-dimensional pore structures are most preferred, as this tends to favour improved diffusion of reactants and products when the catalysts are used for catalysing chemical reactions.
- Incipient wetness impregnation is one method used for preparation of pre-catalysts for methane dehydroaromatization. This method, however, generally presents challenges on an industrial scale.
- the present technology describes a method which is more easily scalable. This method is an acid-base mediated ion exchange, where molybdenum and/or other metals are introduced into zeolite channels by means of simultaneous addition.
- acid-base mediated ion exchange technique relies on the fact that the metals of interest are insoluble at particular pH and that by making the zeolite acidic or basic, the zeolite can act as the counterion when the metal is least soluble and this results in a high loading of the metal within the zeolite channels and attached to the hctcroatoms of the framework.
- Metals introduced into zeolite channels by the simultaneous addition ion exchange method include, but are not limited to, molybdenum, iron, and platinum.
- molybdate anions exist in aqueous solutions as different cluster species, depending on the solution pH and molybdate anion concentration. At high concentrations of molybdate anions and low pH, these clusters contain 4, 6, 7, 8, or more molybdenum ions. Only at high pH does the orthomolybdate ion, [MoO4] 2- , dominate the equilibrium. Due to the small size of the zeolite channels, which are about 5 A, it is thought that only this smallest anion, [MoO4] 2- , can enter the channels.
- the species that exist in solution are controlled by adjusting the pH.
- the approach is to maintain the pH of molybdenum-containing solutions from a pH 7 to 10 and above, to ensure that the smallest anion, [MoO4] 2- , is the dominant form in solution.
- the zeolite slurry may also be acidified to ensure sufficient protonation of reactive anchoring sites on the external and internal surface of the zeolite. This should maintain the desired pH during the ion exchange process by neutralizing the base used to alkalize the molybdenum-containing solution.
- introduction of a molybdate anion into the zeolite requires the surface of zeolite be acidic. Reaction between zeolite and an iron cation requires the conversion of the zeolite to its basic form. Platinum may react with a zeolite under both acidic and basic conditions.
- Simultaneous addition has several advantages over incipient wetness impregnation method because the former allows for more control over the zeolite loading process.
- rate and time may be adjusted by tuning the addition rates of reagents.
- desired pH may be maintained during the course of reaction, which is beneficial to establishing an equilibrium of ion exchange in favor of increasing molybdenum loading in zeolite.
- metals will preferably move into zeolite channels given sufficient time and if added at a controlled rate. Overall, consistent conditions inherent to simultaneous addition help ensure that a more consistent product is made.
- a molybdenum source may be ammonium orthomolybdate, Other sources include, but arc not limited to, ammonium heptamolybdate, or sodium molybdate,
- the molybdate anion source is dissolved in DI water, and the pH of the solution is adjusted with a base to the desired value.
- Bases include, but are not limited to, ammonium hydroxide or sodium hydroxide.
- Iron may be introduced into the zeolite as Fe (II) and/or Fe (III).
- Iron salts include but are not limited to FeSCU, Fe2(SO4)3, and platinum source may be hexachloroplatinic acid, Iron or platinum sources may be added directly to the zeolite slurry or after the molybdenum source has been introduced as a separate solution, with the pH will be adjusted accordingly.
- a solution of molybdate anion and a slurry of zeolite may be mixed together at a rate to maintain the desired pH. After the addition is complete, the slurry will be stirred for given time, filtered and the remaining solid will be air-dried, followed by drying at 110 °C in an oven and calcination at 500 °C for about 5 hr.
- Variations may include: a) Different metal loadings on zeolite support: Mo: 1 - 12 wt%; V: 1 - 10 wt%; W: 1 - 15 wt%; Fe: 0.1 - 1.0 wt%; Ni: 0.1 - 1 wt%; Co: 0.1 - 1 wt%; Zn: 0.1 - 1 wt%; Mn: 0.1 - 1 wt%; Pt: 0.1 - 1 wt%; Cu: 0.1 - 1 wt%; Cr, 0.1 - 1 wt%; Ce, 0.1 - 1 wt%, b) Introduction of metals under varying pH conditions.
- the pH range maintained during simultaneous additions is 0.5 - 6.5; c) Different reaction time and temperature: room temperature, 50 °C; 0.5 - 24 hr; d) Different post-reaction sample treatment: rinsing or not rinsing the material during filtration to wash away undesired ions using DI water or dilute acid solutions; e) Different forms of the zeolite: acidic (HZSM-5) or basic (NH 4 ZSM-5)
- N2 in these reactions was used as an internal standard to calculate methane conversion and benzene selectivity.
- the product gases leaving the reactor were analyzed by an on-line gas chromatograph (Shimadzu GC-2014) that was equipped with a Mol sieve 5 A column to separate H2, N2, CH4 and CO, a Haysep-T column to separate C2 and CO2, and a Haysep- N and a Capillary column to separate C3 and higher hydrocarbons.
- C3 and higher hydrocarbons were detected by an FID detector and all the other gases were detected by a TCD detector.
- the line from the reactor outlet to the GC was maintained at 160°C to avoid any condensation of heavy hydrocarbons.
- Ammonium orthomolybdate (15.9 g, 0.08 mol) was dissolved in 100 mL of DI water in a 250 mL beaker. The pH of the solution was adjusted to 10.0 with ammonium hydroxide.
- iron (II) sulfate heptahydrate (2.61 g, 0.009 mol) was dissolved in 150 mL of DI water and the pH of the solution was adjusted to 0.46 with cone, hydrochloric acid.
- HZSM-5 zeolite 50.1 g was added. The content of both beakers was added simultaneously to a IL beaker containing 50 mL of DI water, using peristaltic pumps.
- the flowrates were adjusted so that addition of both reagents was complete at the same time.
- the pH in the IL beaker was maintained at about 4.4, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary.
- the slurry was stirred for 1 hr, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace.
- the solid material was analyzed using ICP and ICP-MS. The material contained 8.22 wt % of molybdenum and 0.56 wt % of iron.
- Ammonium orthomolybdate (15.8 g, 0.08 mol) was dissolved in 100 mL of DI water in a 250 mL beaker. The pH of the solution was adjusted to 10.0 with ammonium hydroxide.
- iron (II) sulfate heptahydrate (2.61 g, 0.009 mol) was dissolved in 150 mL of DI water and the pH of the solution was adjusted to 0.46 with cone, hydrochloric acid.
- NHaZSM-5 zeolite 50.4 g was added.
- the content of both beakers was added simultaneously to a IL beaker containing 50 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time.
- the pH in the IL beaker was maintained at about 4.0, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary.
- the slurry was stirred for 1 hr, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace.
- the solid material was analyzed using ICP and ICP-MS. The material contained 2.66 wt % of molybdenum and 0.016 wt % of iron.
- Ammonium orthomolybdate (31.3 g, 0.16 mol) was dissolved in 200 mL of DI water in a 600 mL beaker. The pH of the solution was adjusted to 10.0 with ammonium hydroxide.
- HZSM-5 zeolite (100.6 g) was suspended in 300 mL of DI water and the pH was adjusted to 0.56 with cone, hydrochloric acid.
- the content of both beakers was added simultaneously to a IL beaker containing 100 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time.
- the pH in the IL beaker was maintained at about 4.3, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary.
- the slurry was stirred for 16 hr, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace.
- the solid material was analyzed using ICP. The material contained 5.1 wt % of molybdenum.
- Ammonium orthomolybdate (6.14 g, 0.03 mol) was dissolved in 93.6 g of DI water in a 250 mL beaker. The pH of the solution was adjusted to 8.7 with ammonium hydroxide. In a separate 300 mL beaker, HZSM-5 zeolite (10.0 g) was suspended in 90.4 g of DI water, and the pH was adjusted with cone, hydrochloric acid to 2.67. The content of both beakers was added simultaneously to a IL beaker containing 50 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time.
- the pH in the IL heaker was maintained at about 6.4, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary.
- the slurry was stirred for 1 hr, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace.
- the solid material was analyzed using ICP. The material contained 0.93 wt % of molybdenum.
- Ammonium orthomolybdate (30.7 g, 0.16 mol) was dissolved in 150 mL of DI water in a 250 mL beaker. The pH of the solution was adjusted to 9.0 with ammonium hydroxide.
- HZSM-5 zeolite (50.1 g) was suspended in 200 mL of DI water, and the pH was adjusted with cone, hydrochloric acid to 0.04. The content of both beakers was added simultaneously to a IL beaker containing 50 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time.
- the pH in the IL beaker was maintained at about 4.0, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary.
- the slurry was stirred for 1 hr, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace.
- the solid material was analyzed using ICP. The material contained 12.7 wt % of molybdenum.
- Molybdenum oxide (5.66 g, 0.04 mol) was suspended in 75 mL of DI water in a 250 mL beaker. Cone, ammonium hydroxide was added to the suspension to generate ammonium molybdate and to adjust the pH to about 10.
- HZSM-5 zeolite (50.6 g) was suspended in 100 mL of DI water, and the pH was adjusted with cone, hydrochloric acid to 0.28. The content of both beakers was added simultaneously to a 600 mL beaker containing 25 mL of DI water, pre-heated to 50 °C, using peristaltic pumps.
- the flowrates were adjusted so that addition of both reagents was complete at the same time.
- the pH in the 600 mL beaker was maintained at about 4.0 at 50 °C, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary.
- the slurry was stirred for 1 hr, at 50 °C, allowed to cool to room temperature, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace.
- the solid material was analyzed using ICP. The material contained 3.4 wt % of molybdenum.
- Molybdenum trioxide (23.5 g, 0.16 mol) was suspended in 200 mL of DI water in a 600 mL beaker. Cone, ammonium hydroxide was added to the beaker to produce ammonium molybdate and to adjust the pH of the solution to about 9.5.
- HZSM-5 zeolite (100.1 g) was suspended in 300 mL of DI water and the pH was adjusted to 0.10 with cone, hydrochloric acid. The content of both beakers was added simultaneously to a IL beaker containing 100 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time.
- the pH in the IL beaker was maintained at about 4.1, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary.
- a portion of the slurry was sampled after AliC, 2 days, 3, days, 4 days, and 7 days.
- the slurry was filtered, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace.
- the solid material was analyzed using ICP.
- the material contained 3.76 wt% (Ihr), 4.2 wt% (1 day), 9.47 wt% (2 days), 10.44 wt% (3 and 4 days) and 11.18 wt% (7 days) of molybdenum.
- Molybdenum(VI) oxide (11.4 g, 0.08 mol) was suspended in 75 mL of DI water in a 250 mL beaker. Concentrated (50 wt%) sodium hydroxide was added to the beaker to produce sodium molybdate and to adjust the pH to about 11.
- HZSM- 5 (50.1g) zeolite was suspended in 100 mL of DI water. pH of the slurry was adjusted to about 0.5 with cone, nitric acid. The content of both beakers was added simultaneously to a IL beaker containing 25 mL of DI water. The flowrates were adjusted so that both additions were complete at the same time.
- the pH in the IL beaker was maintained at about 4 using small quantities of cone, sodium hydroxide or cone, nitric acid.
- the slurry was stirred for 3hr, the material was filtered, allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace.
- the solid material was analyzed using ICP. The solid contained 1.95 wt% of molybdenum.
- Example 9 The experiment was performed in Example 9, but a solution of iron(III) nitrate (0.92g, 10.29 wt% Fe) was added to the HZSM-5 slurry. The pH during simultaneous addition was maintained at about 4.3. When complete, the slurry was allowed to stir for 3 hr, filtered, dried and calcined as described in Example 7. The material was analyzed by ICP and ICP-MS and determined to contain 2.05 wt% of molybdenum and 0.073 wt% of iron.
- Molybdenum trioxide (22.8 g, 0.16 mol) was added to a beaker containing 150 mL of DI water. Concentrated sodium hydroxide was added to the beaker to produce sodium molybdate and to adjust the pH to about 13.
- a slurry of HZSM-5 zeolite was prepared by suspending zeolite (100 g) in 200 mL of DI water and adjusting the pH with cone, nitric acid to about 0.5. The contents of both beakers were added simultaneously to a 2L beaker containing 50 mL of DI water. The pH during the addition was maintained at about 4.0.
- the content of the beaker was split into 4 equal parts. The first part was filtered off. The second part was washed with 1 wt% nitric acid, the third - using wt5% nitric acid, and the last part using about 15 wt% nitric acid. All four materials were dried and calcined following the protocol described in Example 7. The content of molybdenum in the material was determined by ICP-MS.
- Molybdenum(VI) oxide 11.4 g, 0.08 mol was suspended in 75 mL of DI water in a 250 mL beaker. Concentrated sodium hydroxide (50 wt%) was added to the beaker yielding sodium molybdate and resulting in a pH of about 11.
- metal nitrate solution between 0.4 - 1 g was dissolved in 100 mL of DI water and the pH of the solution was adjusted to about 0.5 - 0.7 with cone, nitric acid acid.
- HZSM-5 zeolite about 50 g was added.
Abstract
The technology relates to a method of preparing a supported molybdenum catalyst, using a simultaneous acid-base mediated ion exchange process and continually monitoring pH, where molybdenum ions are dispersed inside zeolite channels and located in proximity to the acidic aluminum sites. This process leads to high catalytic activity and resistance to deactivation.
Description
ACID-BASE MEDIATED ION-EXCHANGE METAL LOADED ZEOLITE
This application claims priority to U.S. Provisional application 63/328,829, filed April 8, 2022.
Background
[0001] Aromatic compounds are important building blocks of pharmaceuticals, polymers, paints, dyes, explosives, perfumes, and many other materials. Benzene may be the most well-known aromatic compound. Most common methods of production of benzene are not friendly towards the environment, and often require harsh reaction conditions (high temperature, pressure), and the use of expensive catalysts.
[0002] Currently, benzene is predominantly produced from petroleum and coal via catalytic reforming, steam cracking and toluene disproportionation processes, as well as coal processing. Increased demand for lighter hydrocarbon products and decreased North American proportion of liquid petroleum production have led to benzene production growth slowing compared to usage. The gap that has been created requires that the US import about 15% of its benzene from other countries. The value of the imported material is estimated to be almost $1 Billion per year. An alternative method of producing benzene and other aromatic hydrocarbons relies on direct conversion of abundant domestic natural gas feedstocks, mainly methane, and using catalysts based on molybdenum-doped zeolites. This alternative method could utilize methane that is lost due to flaring and leaks. This could potentially have more positive impact on the environment by creating an economically productive disposition for methane. More importantly, the proposed method described herein would place the US in a position of benzene exporter and create an enduring economic benefit.
[0003] Heterogeneous catalysts are used in a vast number of chemical and petrochemical processes. In many cases, the viability of the process depends on the successful combination of the activity of the catalyst and its selectivity and stability. A catalyst that has a high activity but exhibits poor selectivity to the desired products might not be useful to implement a chemical reaction in a commercial scale. Furthermore, a catalyst having a good activity and a good selectivity to the desired product but showing a poor stability may not be suitable for industrial application. An optimum balance between activity,
selectivity and stability must be achieved in order to consider the practical application of a catalyst.
[0004] Small metal or metal oxide particles having diameters in the nanoscale range are often referred to as clusters. There is an advantage in supporting catalytically active metalcontaining clusters on zeolitic materials. Zeolitic materials are unique supports for metal clusters because the steric restrictions imparted by their cages and pores limit the size of the clusters that can form in them. The restrictions imparted by the apertures (often termed “windows”) between cages and pores limit the size of what can enter and leave the pores and cages. Thus clusters can be formed from small precursors (e.g. metal salts) in the cages and be trapped there.
[0005] The cages of zeolitic materials are small enough to exert solvent-like effects on clusters formed within them and thus the cages may induce different catalytic properties to the clusters they contain. Confinement of clusters in zeolitic material cages hinders cluster interactions and aggregation and thereby increase cluster stability.
[0006] Supported metal and metal oxide cluster catalysts can be prepared in a number of different ways. The technology described herein relates to a novel simultaneous addition method for producing molybdenum zeolite cluster catalysts.
Summary
[0007] Molybdenum ions uniformly dispersed inside zeolite channels and located in proximity to the acidic aluminum sites, lead to high catalytic activity and resistance to deactivation in the methane dehydroaromatization process. It is also known that molybdenum solubility varies with pH, with a minimum of around 1.5. A typical procedure is to slurry zeolite ZSM-5 with HC1 at a pH of about 0 - 1, and separately prepare a solution of ammonium molybdate with ammonium hydroxide at a pH of 8 - 11, and then simultaneously introduce the prepared slurry and solution into an ammonium chloride solution at a desirable pH, typically 0.5 - 6.5, where the pH is continually monitored and held constant throughout the procedure by adjusting the relative rates of the slurry and solution throughout the addition.
[0008] This technique is typically referred to as “simultaneous addition” and is regularly used in the chemical industry to produce a consistent product due to the fact that the reaction conditions are maintained and consistent throughout the process. The resulting slurry is filtered and the filtrate is analyzed for molybdenum content. The solid is dried, calcined and analyzed for molybdenum content. Depending on the reaction conditions, anywhere from 1 - 75% of the molybdenum from the initial solution carries through to the filtrate. When the amount of molybdenum in the filtrate is low, it is assumed to be incorporated into the zeolite.
[0009] Analysis of the resulting solids with SEM-EDS qualitatively shows that while some molybdenum is on the surface of the zeolite particle, much of the surface Si and Al are not coated with molybdenum. Thus, the conclusion is that most of the molybdenum is within the zeolite channels.
[0010] In general, this technology is a method of preparing a supported catalyst, comprising the steps of: providing a porous catalyst support comprising a framework having an internal pore structure comprising one or more pores where the internal pore structure comprises a precipitant; adding to the catalyst support a solution or slurry comprising catalytically active molybdate anions such that, on contact with the precipitant, particles comprising the catalytically active metal are precipitated within the internal pore structure of the framework of the catalyst support; and, monitoring the solution pH and adjusting the relative rates of the catalytically active molybdate anions throughout the addition. The catalyst support is typically an aluminosilicate zeolite comprising zeolite channels within the internal pore structure of the framework, and the molybdate anions may be ammonium molybdate anions, which are added to the zeolite channels via a simultaneous acid-base mediated ion exchange process. In this technology, the zeolites may be HZSM- 5 or NH4ZSM-5. In addition to molybdenum, one or more elements selected from the group consisting of iron and platinum may also be used.
[0011] The ammonium molybdate anions may be clusters and have an effective diameter of less than 5.0 nm or less the 2.0 nm. The pH of ammonium molybdate solution or slurry is from 7 to at least 10 and the zeolite is acidified to maintain a desired pH during the ion exchange process, where the zeolite may be acidified with HC1 to a pH of about 0 - 1.
For instance, a solution of ammonium molybdate and ammonium hydroxide is prepared to a pH of 8 - 11 , and is simultaneously introduced to a prepared zeolite slurry or solution into an ammonium chloride solution at a pH of 0.5 - 6.5, and where pH is continually monitored and held constant by adjusting the relative rates of slurry and solution throughout the addition.
[0012] The molybdenum ion source is selected from the group consisting of ammonium orthomolybdate,
ammonium heptamolybdate,
or sodium molybdate,
Brief Description of Figures
[0013] Figure 1 : SEM-EDS images of (left) acid-form zeolite ZSM-5, starting material, and (right) molybdenum-modified zeolite ZSM-5 prepared by acid-base mediated ionexchange.
[0014] Figure 2. Different forms of molybdate anions in aqueous solutions depending on the pH and concentration. (Reprinted from Davantes, A.; Lefevre, G. J. Phys. Chem. A 2013, 117, 12922-12929)
[0015] Figure 3. Acid-base mediated ion exchange loading of acid zeolite.
[0016] Figure 4. Activity Data for 8Mo-0.5Fe/HZSM-5 (Example 1), 2Mo/HZSM-5 (Example 4), and 12Mo/HZSM-5 (Example 5).
Detailed Description
[0017] The internal pore structure of the framework of the catalyst support can be loaded by post-treatment of the catalyst support. The result is a catalyst support in which precipitant is located within the internal pore structure of the framework.
[0018] When the catalyst support is contacted with a solution or colloidal suspension comprising a catalytically active metal, the solution or colloidal suspension enters the internal porous structure of the catalyst support framework and, on contact with precipitant, precipitation or formation of insoluble particles occurs, which particles comprise the catalytically
active metal. Such particles comprising the catalytically active metal are referred to herein as “clusters”. Typically, such clusters have effective diameters of less than 5.0 nm, more preferably less than 2.0 nm, for example less than 1.3 nm. Typically, the maximum dimension or effective diameter of the cluster is defined by the internal pore structure of the catalyst support framework. The catalytically active metal can be dissolved in a solution, or can be a constituent of a colloid in suspension, or both.
[0019] The catalyst support can be crystalline or amorphous, with a preference for crystalline supports due to their well-defined pore structure and generally greater stability. The catalyst support is preferably an inorganic support, and more preferably an oxide support. Examples of oxide supports include silica, alumina, zirconia, titania, ceria, lanthanum oxide, and mixed oxides thereof, such as alumina-silica. Other examples of catalyst supports include those having extended phosphate structures, for example alumino- phosphates, a gallo-phosphates, silico-alumino-phosphates and silico-gallo-phosphates.
[0020] The catalyst support is preferably an oxide material having a zeotype structure, exemplified by zeolites. Numerous zeotype structures are known, and are described in the “Atlas of Zeolite Structures” published and maintained by the International Zeolite Association. Preferred structures are those having a 2-dimensional or 3-dimensional porous network, intersecting at cages having a diameter larger than that of the pores. Examples of zeotype structures having such a 2-dimensional and 3-dimensional pore configuration include CHA, FAU, BEA, MFI, MEL and MWW. 3-dimensional pore structures are most preferred, as this tends to favour improved diffusion of reactants and products when the catalysts are used for catalysing chemical reactions.
[0021] Incipient wetness impregnation is one method used for preparation of pre-catalysts for methane dehydroaromatization. This method, however, generally presents challenges on an industrial scale. The present technology describes a method which is more easily scalable. This method is an acid-base mediated ion exchange, where molybdenum and/or other metals are introduced into zeolite channels by means of simultaneous addition.
[0022] Not being bound by theory, it is thought that acid-base mediated ion exchange technique relies on the fact that the metals of interest are insoluble at particular pH and that by making the zeolite acidic or basic, the zeolite can act as the counterion when the metal is
least soluble and this results in a high loading of the metal within the zeolite channels and attached to the hctcroatoms of the framework.
[0023] Metals introduced into zeolite channels by the simultaneous addition ion exchange method include, but are not limited to, molybdenum, iron, and platinum. As shown in Fig. 2, molybdate anions exist in aqueous solutions as different cluster species, depending on the solution pH and molybdate anion concentration. At high concentrations of molybdate anions and low pH, these clusters contain 4, 6, 7, 8, or more molybdenum ions. Only at high pH does the orthomolybdate ion, [MoO4]2-, dominate the equilibrium. Due to the small size of the zeolite channels, which are about 5 A, it is thought that only this smallest anion, [MoO4]2-, can enter the channels. The species that exist in solution are controlled by adjusting the pH. Thus, the approach is to maintain the pH of molybdenum-containing solutions from a pH 7 to 10 and above, to ensure that the smallest anion, [MoO4]2- , is the dominant form in solution.
[0024] The zeolite slurry may also be acidified to ensure sufficient protonation of reactive anchoring sites on the external and internal surface of the zeolite. This should maintain the desired pH during the ion exchange process by neutralizing the base used to alkalize the molybdenum-containing solution. As shown in Fig. 3, introduction of a molybdate anion into the zeolite requires the surface of zeolite be acidic. Reaction between zeolite and an iron cation requires the conversion of the zeolite to its basic form. Platinum may react with a zeolite under both acidic and basic conditions.
[0025] Simultaneous addition has several advantages over incipient wetness impregnation method because the former allows for more control over the zeolite loading process. First, under simultaneous reaction conditions, rate and time may be adjusted by tuning the addition rates of reagents. Second, desired pH may be maintained during the course of reaction, which is beneficial to establishing an equilibrium of ion exchange in favor of increasing molybdenum loading in zeolite. Third, metals will preferably move into zeolite channels given sufficient time and if added at a controlled rate. Overall, consistent conditions inherent to simultaneous addition help ensure that a more consistent product is made.
[0026] A molybdenum source may be ammonium orthomolybdate,
Other sources include, but arc not limited to, ammonium heptamolybdate, or sodium
molybdate,
The molybdate anion source is dissolved in DI water, and the pH of the solution is adjusted with a base to the desired value. Bases include, but are not limited to, ammonium hydroxide or sodium hydroxide. Iron may be introduced into the zeolite as Fe (II) and/or Fe (III). Iron salts include but are not limited to FeSCU, Fe2(SO4)3,
and
platinum source may be hexachloroplatinic acid,
Iron or platinum sources may be added directly to the zeolite slurry or after the molybdenum source has been introduced as a separate solution, with the pH will be adjusted accordingly.
[0027] Generally, a solution of molybdate anion and a slurry of zeolite may be mixed together at a rate to maintain the desired pH. After the addition is complete, the slurry will be stirred for given time, filtered and the remaining solid will be air-dried, followed by drying at 110 °C in an oven and calcination at 500 °C for about 5 hr. Variations may include: a) Different metal loadings on zeolite support: Mo: 1 - 12 wt%; V: 1 - 10 wt%; W: 1 - 15 wt%; Fe: 0.1 - 1.0 wt%; Ni: 0.1 - 1 wt%; Co: 0.1 - 1 wt%; Zn: 0.1 - 1 wt%; Mn: 0.1 - 1 wt%; Pt: 0.1 - 1 wt%; Cu: 0.1 - 1 wt%; Cr, 0.1 - 1 wt%; Ce, 0.1 - 1 wt%, b) Introduction of metals under varying pH conditions. The pH range maintained during simultaneous additions is 0.5 - 6.5; c) Different reaction time and temperature: room temperature, 50 °C; 0.5 - 24 hr; d) Different post-reaction sample treatment: rinsing or not rinsing the material during filtration to wash away undesired ions using DI water or dilute acid solutions; e) Different forms of the zeolite: acidic (HZSM-5) or basic (NH4ZSM-5)
[0028] Examples:
[0029] General: The metal loaded zeolite precursors described below were tested in the methane dehydroaromatization reaction. The reactions were carried out in a fixed-bed quartz reactor (8 mm i.d.) at 700°C and atmospheric pressure. 0.5 g of sieved catalyst (60 - 120 mesh) was placed in the reactor tube and the catalyst bed was held in place by quartz wool. The catalyst was heated from room temperature to 700°C with a ramp of 5°C/min under CH4+H2 flow. The final samples were then cooled to room temperature and
reheated again in He, then a mixture of CH4 and N2 (9 vol%) was introduced into the reactor through a mass flow controller at a space velocity of 1550 ml/gcat/h. N2 in these reactions was used as an internal standard to calculate methane conversion and benzene selectivity. The product gases leaving the reactor were analyzed by an on-line gas chromatograph (Shimadzu GC-2014) that was equipped with a Mol sieve 5 A column to separate H2, N2, CH4 and CO, a Haysep-T column to separate C2 and CO2, and a Haysep- N and a Capillary column to separate C3 and higher hydrocarbons. C3 and higher hydrocarbons were detected by an FID detector and all the other gases were detected by a TCD detector. The line from the reactor outlet to the GC was maintained at 160°C to avoid any condensation of heavy hydrocarbons. These results are shown in Figure 4.
[0030] Example 1
[0031] Ammonium orthomolybdate (15.9 g, 0.08 mol) was dissolved in 100 mL of DI water in a 250 mL beaker. The pH of the solution was adjusted to 10.0 with ammonium hydroxide. In a separate 300 mL beaker, iron (II) sulfate heptahydrate (2.61 g, 0.009 mol) was dissolved in 150 mL of DI water and the pH of the solution was adjusted to 0.46 with cone, hydrochloric acid. To the same beaker, HZSM-5 zeolite (50.1 g) was added. The content of both beakers was added simultaneously to a IL beaker containing 50 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time. The pH in the IL beaker was maintained at about 4.4, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary. When the addition was complete, the slurry was stirred for 1 hr, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace. The solid material was analyzed using ICP and ICP-MS. The material contained 8.22 wt % of molybdenum and 0.56 wt % of iron.
[0032] Example 2
[0033] Ammonium orthomolybdate (15.8 g, 0.08 mol) was dissolved in 100 mL of DI water in a 250 mL beaker. The pH of the solution was adjusted to 10.0 with ammonium hydroxide. In a separate 300 mL beaker, iron (II) sulfate heptahydrate (2.61 g, 0.009 mol) was dissolved in 150 mL of DI water and the pH of the solution was adjusted to 0.46 with
cone, hydrochloric acid. To the same beaker, NHaZSM-5 zeolite (50.4 g) was added. The content of both beakers was added simultaneously to a IL beaker containing 50 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time. The pH in the IL beaker was maintained at about 4.0, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary. When the addition was complete, the slurry was stirred for 1 hr, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace. The solid material was analyzed using ICP and ICP-MS. The material contained 2.66 wt % of molybdenum and 0.016 wt % of iron.
[0034] Example 3
[0035] Ammonium orthomolybdate (31.3 g, 0.16 mol) was dissolved in 200 mL of DI water in a 600 mL beaker. The pH of the solution was adjusted to 10.0 with ammonium hydroxide. In a separate 600 mL beaker, HZSM-5 zeolite (100.6 g) was suspended in 300 mL of DI water and the pH was adjusted to 0.56 with cone, hydrochloric acid. The content of both beakers was added simultaneously to a IL beaker containing 100 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time. The pH in the IL beaker was maintained at about 4.3, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary. When the addition was complete, the slurry was stirred for 16 hr, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace. The solid material was analyzed using ICP. The material contained 5.1 wt % of molybdenum.
[0036] Example 4
[0037] Ammonium orthomolybdate (6.14 g, 0.03 mol) was dissolved in 93.6 g of DI water in a 250 mL beaker. The pH of the solution was adjusted to 8.7 with ammonium hydroxide. In a separate 300 mL beaker, HZSM-5 zeolite (10.0 g) was suspended in 90.4 g of DI water, and the pH was adjusted with cone, hydrochloric acid to 2.67. The content of both beakers was added simultaneously to a IL beaker containing 50 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was
complete at the same time. The pH in the IL heaker was maintained at about 6.4, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary. When the addition was complete, the slurry was stirred for 1 hr, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace. The solid material was analyzed using ICP. The material contained 0.93 wt % of molybdenum.
[0038] Example 5
[0039] Ammonium orthomolybdate (30.7 g, 0.16 mol) was dissolved in 150 mL of DI water in a 250 mL beaker. The pH of the solution was adjusted to 9.0 with ammonium hydroxide. In a separate 600 mL beaker, HZSM-5 zeolite (50.1 g) was suspended in 200 mL of DI water, and the pH was adjusted with cone, hydrochloric acid to 0.04. The content of both beakers was added simultaneously to a IL beaker containing 50 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time. The pH in the IL beaker was maintained at about 4.0, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary. When the addition was complete, the slurry was stirred for 1 hr, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace. The solid material was analyzed using ICP. The material contained 12.7 wt % of molybdenum.
[0040] Example 6
[0041] Molybdenum oxide (5.66 g, 0.04 mol) was suspended in 75 mL of DI water in a 250 mL beaker. Cone, ammonium hydroxide was added to the suspension to generate ammonium molybdate and to adjust the pH to about 10. In a separate 400 mL beaker, HZSM-5 zeolite (50.6 g) was suspended in 100 mL of DI water, and the pH was adjusted with cone, hydrochloric acid to 0.28. The content of both beakers was added simultaneously to a 600 mL beaker containing 25 mL of DI water, pre-heated to 50 °C, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time. The pH in the 600 mL beaker was maintained at about 4.0 at 50 °C, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary. When the addition was complete, the slurry was stirred for 1 hr, at 50 °C, allowed to cool
to room temperature, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace. The solid material was analyzed using ICP. The material contained 3.4 wt % of molybdenum.
[0042] Example 7
[0043] Molybdenum trioxide (23.5 g, 0.16 mol) was suspended in 200 mL of DI water in a 600 mL beaker. Cone, ammonium hydroxide was added to the beaker to produce ammonium molybdate and to adjust the pH of the solution to about 9.5. In a separate 600 mL beaker, HZSM-5 zeolite (100.1 g) was suspended in 300 mL of DI water and the pH was adjusted to 0.10 with cone, hydrochloric acid. The content of both beakers was added simultaneously to a IL beaker containing 100 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time. The pH in the IL beaker was maintained at about 4.1, and additional cone, hydrochloric acid or ammonium hydroxide was used when necessary. When the addition was complete, a portion of the slurry was sampled after Ihr, 1 day, 2 days, 3, days, 4 days, and 7 days. The slurry was filtered, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace. The solid material was analyzed using ICP. The material contained 3.76 wt% (Ihr), 4.2 wt% (1 day), 9.47 wt% (2 days), 10.44 wt% (3 and 4 days) and 11.18 wt% (7 days) of molybdenum.
[0044] Example 8
[0045] Molybdenum(VI) oxide (11.4 g, 0.08 mol) was suspended in 75 mL of DI water in a 250 mL beaker. Concentrated (50 wt%) sodium hydroxide was added to the beaker to produce sodium molybdate and to adjust the pH to about 11. In a separate 300 mL beaker, HZSM- 5 (50.1g) zeolite was suspended in 100 mL of DI water. pH of the slurry was adjusted to about 0.5 with cone, nitric acid. The content of both beakers was added simultaneously to a IL beaker containing 25 mL of DI water. The flowrates were adjusted so that both additions were complete at the same time. The pH in the IL beaker was maintained at about 4 using small quantities of cone, sodium hydroxide or cone, nitric acid. When the addition was complete, the slurry was stirred for 3hr, the material was filtered, allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and
calcined (500 °C, 5 hr, 1 °C/min) in a furnace. The solid material was analyzed using ICP. The solid contained 1.95 wt% of molybdenum.
[0046] Example 9
[0047] The experiment was performed in a manner described in Example 9, but the pH during the addition was maintained at about 1.0. ICP analysis of the solid after drying and calcination revealed molybdenum content to be about 2.29 wt%.
[0048] Example 10
[0049] The experiment was performed in Example 9, but a solution of iron(III) nitrate (0.92g, 10.29 wt% Fe) was added to the HZSM-5 slurry. The pH during simultaneous addition was maintained at about 4.3. When complete, the slurry was allowed to stir for 3 hr, filtered, dried and calcined as described in Example 7. The material was analyzed by ICP and ICP-MS and determined to contain 2.05 wt% of molybdenum and 0.073 wt% of iron.
[0050] Example 11
[0051] Molybdenum trioxide (22.8 g, 0.16 mol) was added to a beaker containing 150 mL of DI water. Concentrated sodium hydroxide was added to the beaker to produce sodium molybdate and to adjust the pH to about 13. In a separate beaker, a slurry of HZSM-5 zeolite was prepared by suspending zeolite (100 g) in 200 mL of DI water and adjusting the pH with cone, nitric acid to about 0.5. The contents of both beakers were added simultaneously to a 2L beaker containing 50 mL of DI water. The pH during the addition was maintained at about 4.0. After stirring the slurry for 3 hr at ambient temperature, the content of the beaker was split into 4 equal parts. The first part was filtered off. The second part was washed with 1 wt% nitric acid, the third - using wt5% nitric acid, and the last part using about 15 wt% nitric acid. All four materials were dried and calcined following the protocol described in Example 7. The content of molybdenum in the material was determined by ICP-MS.
[0052] Example 12
[0053] Molybdenum(VI) oxide ( 11.4 g, 0.08 mol) was suspended in 75 mL of DI water in a 250 mL beaker. Concentrated sodium hydroxide (50 wt%) was added to the beaker yielding sodium molybdate and resulting in a pH of about 11. In a separate 300 mL beaker, metal nitrate solution (between 0.4 - 1 g) was dissolved in 100 mL of DI water and the pH of the solution was adjusted to about 0.5 - 0.7 with cone, nitric acid acid. To the same beaker, HZSM-5 zeolite (about 50 g) was added. The content of both beakers was added simultaneously to a 1L beaker containing 25 mL of DI water, using peristaltic pumps. The flowrates were adjusted so that addition of both reagents was complete at the same time. The pH in the IL beaker was maintained at about 4.0, and additional cone, nitric acid or sodium hydroxide was used when necessary. When the addition was complete, the slurry was stirred for 3 hr, the material was filtered and allowed to dry in open air overnight. Next, the material was dried (110 °C, 2 hr, 1 °C/min) and calcined (500 °C, 5 hr, 1 °C/min) in a furnace. The solid material was analyzed using ICP and ICP-MS.
[0054] Example 13
[0055] Activity data for the 8 wt % Mo and 0.6 wt % Fe (Example 1), 1 wt % Mo (Example 4) and 12 wt % Mo (Example 5) catalysts is shown in Figure 4.
Claims
1. A method of preparing a supported catalyst, comprising the steps of:
(i) providing a porous catalyst support comprising a framework having an internal pore structure comprising one or more pores where the internal pore structure comprises a precipitant;
(ii) adding to the catalyst support a solution or slurry comprising catalytically active molybdate anions such that, on contact with the precipitant, particles comprising the catalytically active metal are precipitated within the internal pore structure of the framework of the catalyst support, and;
(iii) monitoring the solution pH and adjusting the relative rates of the catalytically active molybdate anions throughout the addition.
2. The method according to claim 1, where the catalyst support is an aluminosilicate zeolite comprising zeolite channels within the internal pore structure of the framework.
3. The method of claim 1 wherein the molybdate anions are ammonium molybdate anions.
4. The method according to claim 3 wherein the ammonium molybdate anions are added to the zeolite channels via a simultaneous acid-base mediated ion exchange process.
5. The method according to claim 4, where the ammonium molybdate anions are clusters and have an effective diameter of less than 5.0 nm.
6. The method according to claim 4, where the ammonium molybdate anions are clusters and have an effective diameter of less than 2.0 nm.
7. The method according to claim 4, where the pH of ammonium molybdate solution or slurry is from 7 to at least 10.
8. The method of claim 2, where the zeolite is acidified to maintain a pH during the ion exchange process.
9. The method of claim 8, where zeolite is acidified with HC1 to a pH of about 0 - 1.
10. The method of claim 1 wherein a solution of ammonium molybdate and ammonium hydroxide is prepared to a pH of 8 - 11, and is simultaneously introduced to a prepared zeolite slurry or solution into an ammonium chloride solution at a pH of 0.5 - 6.5.
11. The method of claim 9, where the pH is continually monitored and held constant by adjusting the relative rates of slurry and solution throughout the addition.
12. The method of claim 4, where the pH range maintained during simultaneous additions is 0.5 - 6.5.
13. The method of claim 1, wherein the molybdenum is selected from the group consisting of ammonium orthomolybdate, (NH4)2MoO4, ammonium heptamolybdate, (NH4)6MovO24, or sodium molybdate, Na2MoO4.
14. The method of claim 1, wherein the zeolite is HZSM-5.
15. The method of claim 1, wherein the zeolite is NH4ZSM-5.
16. The method of claim 1, additionally comprising contacting the catalyst support with iron.
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Title |
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DAVANTES, A.LEFEVRE, G., J. PHYS. CHEM. A, vol. 117, 2013, pages 12922 - 12929 |
DENARDIN FELIPE G. ET AL: "Methane dehydroaromatization over Fe-M/ZSM-5 catalysts (M= Zr, Nb, Mo)", MICROPOROUS AND MESOPOROUS MATERIALS, vol. 295, 1 March 2020 (2020-03-01), Amsterdam ,NL, pages 109961, XP093058375, ISSN: 1387-1811, DOI: 10.1016/j.micromeso.2019.109961 * |
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